The Japanese attack on Pearl Harbor

: : : : : It's impossible to determine in which direction the airplanes are headed from the information given.
: : : : : The observer (presumably on Oahu) has only stated that by looking to the east-northeast, he/she saw airplanes about 210 kilometers away.

: : : Hi, sphinx. In this instance, it was EAH who erased your original question, so you can see how doing so confuses the thread. What you had asked was,
: : : "'A reporter at a detector station out in the Pacific saw a large flight of airplanes about 210 kilometers from Oahu to the east-northeast.'

: : : (What ON EARTH direction are Japanese airplanes flying in? Are they from the east-northeast, or are they flying east-northeast?)"

: : : EAH is entirely correct in saying that seeing the planes in a given direction from the viewer gives no indication of the direction in which they were flying, but I understood your original question to be, what does the word "to" mean in this context? It means "in the direction of" east-northeast from the observer. Thus, assuming the reporter saw the planes on their approach, they were coming from E-NE. But even if the reporter only saw them on their return, or while they were circling around for their best bombing approach, they were "to" the reporter's E-NE, that is, E-NE from the reporter.

: :
: : Japanese planes, of course, should emerge from the west!

: Ha! Of course you're right. But then, I'm not sure where the fleet was standing. And the planes might have been circling, but 210km seems like an awfully wide circle. If your source is correct, though, the planes were reported to be coming from the direction of California.

[Vice-Admiral] Nagumo's fleet assembled in the remote anchorage of Tankan Bay in the Kurile Islands and departed in strictest secrecy for Hawaii on November 26th. The ships' route crossed the North Pacific and avoided normal shipping lanes. At dawn on December 7th the task force had approached undetected to a point slightly more than 200 miles north of Oahu.
At 7:02 am the alert operator of an Army radar station at Opana spotted the approaching first wave of the attack force. The officers to whom those reports were relayed did not consider them significant enough to take urgent action. http://www.scs.k12.tn.us/pearl_harbor_webquest/background_information.htm

7:02am - Opana Radar Station privates Joseph Lockhard & George Elliott sight Japanese planes 132 mi. northeast (1st wave had taken off from carriers at 6:00am 230 miles away).
http://history.acusd.edu/gen/WW2Timeline/Prelude23.html